Maxim MAX1688EUE, MAX1688ESA, MAX1687ESA Datasheet

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General Description

The MAX1687/MAX1688 step-up DC-DC converters deliv­er up to 2W from a single Li-Ion or three NiMH cells. The
devices are ideal for burst-load applications such as GSM
cell phones and wireless LANs, where the RF power
amplifiers require short, high current bursts. The
MAX1687/MAX1688 reduce battery surge current by slow­ly charging a reservoir capacitor, which supplies the nec­essary peak energy for the load current burst. As a result,
the peak battery current is limited, thus maximizing battery
life and minimizing battery voltage sag and transient dips.

An internal synchronous rectifier provides over 90% con­version efficiency and eliminates the need for an external
Schottky diode. A logic shutdown mode reduces the shut­down current to only 3µA. The devices can be disabled
during current bursts (RF transmit mode) to eliminate
switching noise.

The switching frequency of the MAX1687/MAX1688, con­trolled by the selected inductor, can exceed 1MHz. Two
external resistors set the output voltage from 1.25V to 6V.
The MAX1687 controls peak battery current, while the
MAX1688 features a more advanced, adaptive constant­recharge-time algorithm that maximizes battery life. The
MAX1687/MAX1688 are available in thin 16-pin TSSOP
(1.1mm max height) or standard 8-pin SO packages.

Applications

GSM Phones
Wireless Handsets
PC Cards (PCMCIA)

Features

♦ Low 450mA Peak Battery Current

Provides 2A, 5V GSM Burst

♦ 90% Efficiency
♦ Internal Power MOSFETs and Current-Sense

Resistor

♦ Output Disconnects from Input During Shutdown
♦ 3µA Shutdown Current
♦ Precise Voltage-Controlled Current Limit

(MAX1687)

♦ Adaptive Constant-Recharge-Time Capability

(MAX1688)

♦ 1.25V to 6V Adjustable Output
♦ 2.7V to 6V Input Range

(1 Li-Ion cell or 3 NiMH cells)

♦ Switching Frequency Can Exceed 1MHz
♦ Standby Mode Disables DC-DC During

Transmission Burst

♦ Low Inrush Current at Start-Up

MAX1687

†

/MAX1688

†

Step-Up DC-DC Converters with

Precise, Adaptive Current Limit for GSM

________________________________________________________________

Maxim Integrated Products

1

16
15
14
13
12
11
10

9

1
2
3
4
5
6
7
8

IN OUT

OUT
LX2
LX2
PGND
PGND
AGND
ON

TOP VIEW

MAX1687
MAX1688

TSSOP

IN

LX1

FB

LX1

LIM [CHG]

REF

N.C.

[ ] ARE FOR MAX1688

Typical Operating Circuit

19-1426; Rev 0; 2/99

PART*

MAX1687EUE

MAX1687ESA
MAX1688EUE

-40°C to +85°C

-40°C to +85°C

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

16 TSSOP
8 SO
16 TSSOP

Pin Configurations

Ordering Information

MAX1688ESA -40°C to +85°C

8 SO

Pin Configurations continued at end of data sheet.

†

Patent pending

*

U.S. and foreign patents pending.

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

2.7V TO 6V

1 Li-lon

OR

3 NiMH

OR

3 ALKALINE

ON

OFF

0 TO 1V

CONTROL INPUT

( ) ARE FOR MAX1687
[ ] ARE FOR MAX1688

LX1 LX2

IN

MAX1687
MAX1688

ON
(LIM)

REF

GND

OUT

FB

[CHG]

V

OUT

UP TO 6V

MAX1687/MAX1688

Step-Up DC-DC Converters with
Precise, Adaptive Current Limit for GSM

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= VON= +3V, V

LIM

= 1V (MAX1687), V

CHG

= 1V (MAX1688), VFB= 1.5V, V

OUT

= 6V, TA = 0°C to +85°C, unless otherwise noted.

Typical values are at T

A

= +25°C.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

IN, ON, LX1, CHG, LIM, FB, OUT, REF to GND.......-0.3V to +7V

LX2 to GND ..............................................................-0.3V to +8V

IN, LX1 Average Current..........................................................1A

Continuous Power Dissipation (TA= +70°C)

TSSOP (derate 5.7mW/°C above +70°C) ....................457mW

SO (derate 5.88mW/°C above +70°C).........................471mW

Operating Temperature Range ...........................-40°C to +85°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10sec)............................+300° C

IN rising, 1% hysteresis

VFB= 0, V

OUT

= 3V (MAX1688)

VFB= 1.125V, V

OUT

= 3V (MAX1688)

VFBrising, 2% hysteresis

I

REF

= 0 to 10µA

VFB= 1.5V
Shutdown, VIN= 4.2V, LX2 connected to LX1,

V

OUT

= 0, ON = GND

V

LIM

= V

CHG

= 1V

CONDITIONS

0.744 0.8 0.856

Peak Current

VV

REF

6Output Voltage Range

V

2.4 2.5 2.6

V2.7 6Input Voltage Range

Input Undervoltage Lockout

µA60 110I

CHG

Source Current

mmho0.18 0.2 0.22g

mFB

FB Transconductance

V1.212 1.250 1.288FB Set Voltage

V1.225 1.25 1.275V

REF

Reference Voltage

mA

24

Input Supply Current

µA310

UNITSMIN TYP MAXSYMBOLPARAMETER

V

LIM

= V

CHG

= 1V

V

LIM

= V

CHG

= 0.65V

VIN= 2.7V

V

LIM

= 1V

VON= 0 or 3V

VIN= 2.7V
VIN= 6V
VIN= 4.2V
VFB= 1.5V

VIN= 2.7V Ω0.3 0.7P-Channel On-Resistance

Ω0.1 0.18R

SENSE

Sense Resistor

mA170 200 230I

RIPPLE

A

0.46 0.5 0.54

I

PEAK

Ripple Current

Ω0.4 0.8N-Channel On-Resistance

2

0.02 0.1

I

LIM

0.02 0.1I

ON

V0.6V

IL

V

1.8

ON Input Low Voltage

1.5

0.05 0.2I

FB

Input Current

VIN= V

LX2

= 6V, V

OUT

= VON= 0

VIN= 4V, V

FB

= 0, V

OUT

= 0

µA0.05 10

Ω30 70Precharge On-Resistance

LX2 Leakage Current

ms0.7 1.2 1.8t

DELAY

Shutdown Delay

V

IH

ON Input High Voltage

µA

TA= 0°C to +85°C

TA= +25°C

MAX1687/MAX1688

Step-Up DC-DC Converters with

Precise, Adaptive Current Limit for GSM

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS

(VIN= VON= +3V, V

LIM

= 1V (MAX1687), V

CHG

= 1V (MAX1688), VFB= 1.5V, V

OUT

= 6V, TA= -40°C to +85°C, unless otherwise noted.)

(Note 1)

Note 1: Specifications to -40°C are guaranteed by design, not production tested.

V

LIM

= V

CHG

= 1V

V

LIM

= V

CHG

= 0.65V

I

IN

IN rising, 1% hysteresis

VFB= 1.125V, V

OUT

= 3V (MAX1688)

FB rising, 2% hysteresis

I

REF

= 0 to 10µA

VFB= 1.5V
Shutdown VIN= 4.2V, LX2 connected to LX1,

V

OUT

= 0, ON = GND

V

LIM

= V

CHG

= 1V

CONDITIONS

mA

145 240

I

RIPPLE

Ripple Current

A

0.44 0.57

I

PEAK

Ω

0.18

R

SENSE

Sense Resistor

0.73 0.90

Peak Current

V

2.35 2.65

V

2.7 6

Input Voltage Range
Input Undervoltage Lockout

mmho

0.16 0.24

gm

FB

FB Transconductance

V

1.20 1.30

FB Set Voltage

V1.212 1.288V

REF

Reference Voltage

ms

0.6 2

T

DELAY

Shutdown Delay

mA

5

I

SHDN

Input Supply Current

µA10

UNITSMIN TYP MAXSYMBOLPARAMETER

VIN= 4V, V

FB

= 0, V

OUT

= 0

VIN= 2.7V

VIN= 2.7V

Ω

70

Precharge On-Resistance

Ω

0.7

Ω

0.8

N-Channel On-Resistance
P-Channel On-Resistance

Typical Operating Characteristics

(VIN= +3.3V, V

OUT

= 5V, V

LIM

= 1V, Figures 6b and 7, TA= +25°C, unless otherwise noted.)

60

70

65

80

75

85

95
90

0 150 20050 100 250 300 350

EFFICIENCY vs. DC LOAD CURRENT

(V

OUT

= 5.5V)

MAX1687/88 toc01

LOAD CURRENT (mA)

EFFICIENCY (%)

VIN = 5V

VIN = 3.3V

VIN = 2.7V

VIN = 6V

60

65

70

75

80

85

90

95

0 1500500 1000 2000 2500 3000

EFFICIENCY vs. GSM BURST LOAD

(V

OUT

= 5.5V)

MAX1687/88 toc02

LOAD CURRENT (mA)

EFFICIENCY (%)

VIN = 5V

VIN = 3.3V

VIN = 2.7V

VIN = 6V

60

70
65

80
75

95
90
85

100

0 10050 150 200 250 300 350

EFFICIENCY vs. LOAD CURRENT

(V

IN

= 2.7V, V

OUT

= 3.3V)

MAX1687/88 toc03

LOAD CURRENT (mA)

EFFICIENCY (%)

VIN= 2.7V V

0.6

V

IL

ON Input Low Voltage

V

VIN= 6V
VIN= 4.2V

V

IH

ON Input High Voltage

1.8

1.5

V

V

REF

6

Output Voltage Range

MAX1687/MAX1688

Step-Up DC-DC Converters with Precise,
Adaptive Current Limit for GSM

4 _______________________________________________________________________________________

_____________________________

Typical Operating Characteristics (continued)

(V

IN

= +3.3V, V

OUT

= 5V, V

LIM

= 1V, Figures 6b and 7, TA= +25°C, unless otherwise noted.)

300

450
400
350

500

550

600

650

700

750

800

100 200150 250 300 350 400

MAX1688

I

PEAK

vs. V

OUT

DROOP

MAX1687/88 toc09

V

OUT

DROOP (mV)

I

PEAK

(mA)

R

CHG

= 40.2k

0

800
700
600
500
400
300
200

100

15 20 25 30 35 40

MAX1688 PEAK INDUCTOR CURRENT

vs. R

CHG

(1A GSM LOAD)

MAX1687/88 toc10

R

CHG

(kΩ)

PEAK INDUCTOR CURRENT (mA)

0

100

200

300

400

500

600

700

800

15 20 25 30 35 40

MAX1688 PEAK BATTERY CURRENT

vs. R

CHG

(1A GSM LOAD)

MAX1687/88 toc04

R

CHG

(kΩ)

PEAK BATTERY CURRENT (mA)

1.5

2.5

2.0

3.5

3.0

4.0

4.5

-40 20 40-20 0 60 80 100
TEMPERATURE (°C)

SUPPLY CURRENT (mA)

NO-LOAD BATTERY INPUT CURRENT vs.
TEMPERATURE (V

OUT

= 5V, V

LIM

= 1V )

MAX1687/88 toc05

VIN = 5V

VIN = 3.3V

VIN = 2.7V

VIN = 6V

REFERENCE VOLTAGE vs. REFERENCE

CURRENT (V

IN

= 3.3V, V

OUT

= 5V)

MAX1687/88 toc06

I

REF

(µA)

V

REF

(V)

1.245

1.200
1 100010010

1.215

1.205

1.235

1.225

1.250

1.220

1.210

1.240

1.230

1.245

1.247

1.249

1.251

1.253

TEMPERATURE (°C)

REFERENCE VOLTAGE (V)

-40 20 40-20 0 60 80 100

REFERENCE VOLTAGE vs. TEMPERATURE

(V

IN

= 3.3V, V

OUT

= 5V)

MAX1687/88 toc07

1200

0

1 10 100

SWITCHING FREQUENCY vs. INDUCTANCE

(V

IN

= 3.3V, V

OUT

= 5V,

I

LOAD

= 100mA, V

LIM

= 1V)

200

MAX1687/88 toc08

INDUCTANCE (µH)

FREQUENCY (kHz)

600

400

1000

800